Stackable

Stacking

Stored items are often stackable: meaning that multiple units of the same item require no more additional space or inventory slots than for a single unit.

As of Update 17 - The Siege of Minas Tirith, which released on October 27, 2015 the stackable size for all crafting materials was increased to 500, allowing significant reduction in storage required for crafting materials.

Additional item units are stacked by default: allowing an item-stack to be treated as a single item for the purposes of inventory storage.

Unstacking

While additional item units are stacked by default: players can choose to unstack one or more units from the stack into an empty storage or inventory slot at any time. To unstack one or more units: left-click the stack while holding down the shift key and drag to an empty inventory slot. This brings up the unstack pop-up dialogue.

Examples

Bronze ingots are a stackable crafting item which stack to 500. This means that - by default - the first 500 bronze ingots a player stores will stack and consume only a single storage slot.

Whereas some other items like, Barrow-treasure are a stackable reputation item which stack to 100.